One-component polyurethane coating and process for its preparation

Abstract

The application relates to the technical field of paint, in particular to a single-component polyurethane paint and a preparation method thereof; the single-component polyurethane paint comprises the following components in parts by weight: 100 parts of polyether polyol, 40-45 parts of diphenylmethane diisocyanate, 25-30 parts of modified castor oil, 15-18 parts of reinforcing filler, 1.0-1.5 parts of light stabilizer and 0.1-0.2 parts of organic tin catalyst. The single-component polyurethane paint solves the problems that the reinforcing filler is prone to sedimentation and the storage stability is poor through the design of the modified castor oil and the optimization of the formula, the process flow is simple and easy to implement, the coating shows excellent adhesion, and the strict requirements for high-performance coating in many fields such as textile shoes and clothes, automobiles and buildings can be fully met.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a single-component polyurethane coating and its preparation method. Background Technology

[0002] Polyurethane coatings are widely used in construction, automotive, and industrial protection fields due to their excellent abrasion resistance, chemical resistance, elasticity, and adhesion. While traditional two-component polyurethane coatings offer superior performance, they require precise metering and mixing, have complex application processes, and a short pot life, limiting their application in certain areas. In contrast, single-component polyurethane coatings do not require on-site mixing, offer good storage stability, and are easy to apply, thus gaining market favor.

[0003] Traditional reinforcing fillers tend to agglomerate in single-component polyurethane systems, affecting coating uniformity and mechanical properties. Therefore, developing a single-component polyurethane coating that combines excellent weather resistance, high mechanical strength, good application performance, and storage stability is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a single-component polyurethane coating and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a single-component polyurethane coating, comprising the following components by weight: 100 parts of polyether polyol, 40-45 parts of diphenylmethane diisocyanate, 25-30 parts of modified castor oil, 15-18 parts of reinforcing filler, 1.0-1.5 parts of light stabilizer, and 0.1-0.2 parts of organotin catalyst;

[0006] The preparation method of the modified castor oil includes the following steps: 100 parts of castor oil are dehydrated at 120℃ and 1.3kPa vacuum until the water content is ≤0.03%; the dehydrated castor oil, 18 parts of itaconic acid, 0.7 parts of p-toluenesulfonic acid, 0.1 parts of hydroquinone, 0.3 parts of tetraisopropyl titanate and 50 parts of toluene are added to the reaction vessel, and the mixture is azeotropically reacted at 140℃ until the acid value is ≤15mg KOH / g; the temperature is lowered to 70℃, 6 parts of acrylic acid-terminated polyphosphate are added, and the mixture is reacted until the acid value is ≤8mg KOH / g; 15 parts of hyperbranched polyester Boltron H2O, 5 parts of methyl methacrylate, 3 parts of 2-acrylamide-2-methylpropanesulfonic acid and 0.2 parts of cumene hydroperoxide are added, and the mixture is reacted at 85℃ for 3 hours to obtain a light yellow liquid, which is the modified castor oil;

[0007] The reinforcing filler comprises the following components by weight: 12-15 parts nano-alumina, 3-5 parts precipitated barium sulfate, and 0.3-0.5 parts fumed silica.

[0008] Optionally, the hydroxyl value of the polyether polyol is 300-500 mg KOH / g.

[0009] Optionally, the NCO index in the diphenylmethane diisocyanate is 1.05 to 1.15.

[0010] Optionally, the castor oil has a hydroxyl value of 160-168 mg KOH / g and a ricinoleic acid content of ≥85%.

[0011] Optionally, the light stabilizer comprises the following components by weight: 0.5 parts of 2-hydroxy-4-n-octyloxybenzophenone and 0.8 parts of hindered amine light stabilizer, wherein the hindered amine light stabilizer is Tinuvin 123 or Tinuvin 292.

[0012] Optionally, the organotin catalyst is dibutyltin dilaurate.

[0013] Optionally, the average particle size of nano-alumina in the reinforcing filler is 20-50 nm, the average particle size of precipitated barium sulfate is 0.5-2.0 μm, and the average particle size of fumed silica is 10-20 nm.

[0014] On the other hand, the present invention also provides the following technical solution: a method for preparing a single-component polyurethane coating, comprising the following steps:

[0015] S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 800-1000 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 20-30 min to obtain the premix.

[0016] S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 500-600 rpm for 60 min to obtain polyurethane prepolymer;

[0017] S3. Add a light stabilizer to the polyurethane prepolymer and mix at 300-400 rpm for 15 min to obtain a primary coating.

[0018] S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment. The degassing time is 30-60 minutes. Filter the coating through a 200-mesh sieve to obtain the single-component polyurethane coating.

[0019] Optionally, the working pressure of the vacuum degassing is 0.02 to 0.09 MPa.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention solves the problems of easy sedimentation and poor storage stability of reinforcing fillers in single-component polyurethane coatings by designing and optimizing the modified castor oil. The process is simple and easy to implement, and the coating exhibits excellent adhesion, which can fully meet the stringent requirements of high-performance coating in many fields such as textiles, footwear, automobiles, and construction.

[0022] 2. In this invention, fumed silica, with its high specific surface area and surface activity, can construct a three-dimensional network structure in the coating system, thereby significantly improving the viscosity and thixotropy of the coating. When used in conjunction with nano-alumina, this network structure can further enhance the stability of the coating, laying a solid foundation for optimizing the coating performance.

[0023] 3. In this invention, fumed silica can fill the gaps between precipitated barium sulfate particles, constructing a denser filler stacking structure, thereby effectively improving the hardness and wear resistance of the coating film. Nano-alumina adheres to the surface of precipitated barium sulfate particles through intermolecular forces, increasing its surface roughness and reducing the tendency of particles to pack tightly together, thus further optimizing the rheological properties of the coating. This results in better fluidity and thixotropy during construction, providing a strong guarantee for high-quality coating operations. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1: The present invention provides a single-component polyurethane coating comprising the following components by weight: 100 parts of polyether polyol, 40 parts of diphenylmethane diisocyanate, 25 parts of modified castor oil, 15 parts of reinforcing filler, 1.0 part of light stabilizer, and 0.1 parts of organotin catalyst.

[0026] The hindered amine light stabilizer is Tinuvin 123, and the reinforcing filler includes the following components by weight: 12 parts nano alumina, 5 parts precipitated barium sulfate, and 0.5 parts fumed silica.

[0027] The preparation method of the above-mentioned one-component polyurethane coating includes the following steps:

[0028] S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 800 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 20 min to obtain the premix.

[0029] S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 500 rpm for 60 min to obtain polyurethane prepolymer.

[0030] S3. Add a light stabilizer to the polyurethane prepolymer and mix at 300 rpm for 15 min to obtain a primary coating.

[0031] S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment for 30 minutes. Filter the coating through a 200-mesh sieve to obtain a single-component polyurethane coating.

[0032] Example 2: The present invention provides a single-component polyurethane coating comprising the following components by weight: 100 parts of polyether polyol, 42 parts of diphenylmethane diisocyanate, 27 parts of modified castor oil, 17 parts of reinforcing filler, 1.3 parts of light stabilizer, and 0.2 parts of organotin catalyst.

[0033] The hindered amine light stabilizer is Tinuvin 123, and the reinforcing filler includes the following components by weight: 13 parts nano alumina, 4 parts precipitated barium sulfate, and 0.4 parts fumed silica.

[0034] The preparation method of the above-mentioned one-component polyurethane coating includes the following steps:

[0035] S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 900 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 25 min to obtain the premix.

[0036] S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 550 rpm for 60 min to obtain polyurethane prepolymer;

[0037] S3. Add a light stabilizer to the polyurethane prepolymer and mix at 350 rpm for 15 min to obtain a primary coating.

[0038] S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment for 45 minutes. Filter the coating through a 200-mesh sieve to obtain a single-component polyurethane coating.

[0039] Example 3: The present invention provides a single-component polyurethane coating comprising the following components by weight: 100 parts of polyether polyol, 48 parts of diphenylmethane diisocyanate, 28 parts of modified castor oil, 16 parts of reinforcing filler, 1.2 parts of light stabilizer, and 0.1 parts of organotin catalyst.

[0040] The hindered amine light stabilizer is Tinuvin 123, and the reinforcing filler includes the following components by weight: 14 parts nano alumina, 4 parts precipitated barium sulfate, and 0.4 parts fumed silica.

[0041] The preparation method of the above-mentioned one-component polyurethane coating includes the following steps:

[0042] S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 900 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 25 min to obtain the premix.

[0043] S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 550 rpm for 60 min to obtain polyurethane prepolymer;

[0044] S3. Add a light stabilizer to the polyurethane prepolymer and mix at 360 rpm for 15 min to obtain a primary coating.

[0045] S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment for 50 minutes. Filter the coating through a 200-mesh sieve to obtain a single-component polyurethane coating.

[0046] Example 4: The present invention provides a single-component polyurethane coating comprising the following components by weight: 100 parts of polyether polyol, 45 parts of diphenylmethane diisocyanate, 30 parts of modified castor oil, 18 parts of reinforcing filler, 1.5 parts of light stabilizer, and 0.2 parts of organotin catalyst.

[0047] The hindered amine light stabilizer is Tinuvin 292, and the reinforcing filler includes the following components by weight: 15 parts nano alumina, 3 parts precipitated barium sulfate, and 0.3 parts fumed silica.

[0048] The preparation method of the above-mentioned one-component polyurethane coating includes the following steps:

[0049] S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 1000 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 30 min to obtain the premix.

[0050] S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 600 rpm for 60 min to obtain polyurethane prepolymer;

[0051] S3. Add a light stabilizer to the polyurethane prepolymer and mix at 400 rpm for 15 min to obtain a primary coating.

[0052] S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment for 60 minutes. Filter the coating through a 200-mesh sieve to obtain a single-component polyurethane coating.

[0053] To address the issue of reinforcing fillers easily settling in one-component polyurethane coatings, Examples 1-4 propose modified castor oil as a dispersant for reinforcing fillers in one-component polyurethane coatings. The preparation method of modified castor oil includes the following steps: 100 parts of castor oil are dehydrated at 120°C and 1.3 kPa vacuum until the moisture content is ≤0.03%; the dehydrated castor oil, 18 parts itaconic acid, 0.7 parts p-toluenesulfonic acid, 0.1 parts hydroquinone, 0.3 parts tetraisopropyl titanate, and 50 parts toluene are added to a reaction vessel, and the mixture is azeotropically reacted at 140°C until the acid value is ≤15 mg KOH / g; the temperature is lowered to 70°C, and 6 parts of acrylic-terminated polyphosphate are added, reacting until the acid value is ≤8 mg KOH / g; finally, 15 parts of hyperbranched polyester Boltron are added. H2O, 5 parts methyl methacrylate, 3 parts 2-acrylamide-2-methylpropanesulfonic acid and 0.2 parts cumene hydroperoxide were reacted at 85°C for 3 hours to obtain a pale yellow liquid, which is the modified castor oil.

[0054] In Examples 1-4, the hydroxyl value of the polyether polyol was 300-500 mg KOH / g. The NCO index of the diphenylmethane diisocyanate was 1.05-1.15. The hydroxyl value of the castor oil was 160-168 mg KOH / g, and the ricinoleic acid content in the castor oil was ≥85%. The light stabilizer, by weight, included the following components: 0.5 parts of 2-hydroxy-4-n-octyloxybenzophenone and 0.8 parts of hindered amine light stabilizer. The organotin catalyst was dibutyltin dilaurate. The average particle size of the reinforcing filler nano-alumina was 20-50 nm, the average particle size of the precipitated barium sulfate was 0.5-2.0 μm, the average particle size of the fumed silica was 10-20 nm, and the working pressure of the vacuum degassing was 0.02-0.09 MPa.

[0055] Comparative Example 1

[0056] It is basically the same as Example 2, except that modified castor oil was not used.

[0057] Comparative Example 1

[0058] It is basically the same as Example 2, except that castor oil is used instead of modified castor oil. The castor oil has the same specifications as the castor oil used in the preparation of modified castor oil.

[0059] Experimental Example 1

[0060] Test contents: Take the single-component polyurethane coatings prepared in Examples 1 to 4, and then apply them to the surface of the tinplate with a paint brush. When the tinplate is tilted and turned, the coating on the surface does not flow or drip, and a uniform coating film is formed, which is considered qualified. With the side with resin coating facing up, place the tinplate at a temperature of (23±2)℃ and a relative humidity of (50±5)%. Use the finger touch method to measure its surface curing time and record it in Table 1.

[0061] Experimental Example 2

[0062] Test content: According to the method disclosed in GB / T 9286-2021, cross-cut adhesion tests were conducted on colored paints and varnishes at a temperature of (23±2)℃ and a relative humidity of (50±5)%. The coating adhesion grades of the single-component polyurethane coatings prepared in Examples 1 to 4 were tested and recorded in Table 1.

[0063] Table 1

[0064] Surface curing time Coating adhesion rating Example 1 30h45min Level 0 Example 2 28h50min Level 0 Example 3 30h30min Level 0 Example 4 29h20min Level 0

[0065] A coating adhesion rating of 0 indicates that the cut edges are completely smooth and there is no peeling within the grid.

[0066] As shown in Table 1, the single-component polyurethane coating prepared by the invention exhibits excellent coating adhesion and can achieve surface curing within 31 hours at room temperature.

[0067] Experimental Example 3

[0068] Experimental Procedure: The single-component polyurethane coatings prepared in Examples 1-4, and Comparative Examples 1 and 2, were tested for viscosity using a Bollerfeld DV2T fully automatic digital display Brinell rotational viscometer. Each single-component polyurethane coating was placed in a 10L transparent plastic container. The containers were then placed in a closed environment at 25±2℃. After 7 days, the presence of sedimentation was observed and recorded, and the viscosity was measured again. The results are recorded in Table 2. Viscosity change rate = (final viscosity - initial viscosity) / initial viscosity × 100%.

[0069] Table 2

[0070]

[0071] As shown in Table 2, the viscosity change rate of the single-component polyurethane coatings prepared in Examples 1-4 after 7 days was <10%, indicating that the single-component polyurethane coatings prepared by this invention exhibit excellent viscosity stability. None of the single-component polyurethane coatings prepared in Examples 1-4 produced precipitation after 7 days of storage. The modified castor oil prepared by this invention can effectively disperse nano-alumina, precipitated barium sulfate, and fumed silica, thereby improving storage stability.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A one-component polyurethane coating, characterized in that, The product comprises the following components by weight: 100 parts polyether polyol, 40-45 parts diphenylmethane diisocyanate, 25-30 parts modified castor oil, 15-18 parts reinforcing filler, 1.0-1.5 parts light stabilizer, and 0.1-0.2 parts organotin catalyst. The preparation method of the modified castor oil includes the following steps: 100 parts of castor oil are dehydrated at 120℃ and 1.3kPa vacuum until the water content is ≤0.03%; the dehydrated castor oil, 18 parts of itaconic acid, 0.7 parts of p-toluenesulfonic acid, 0.1 parts of hydroquinone, 0.3 parts of tetraisopropyl titanate and 50 parts of toluene are added to the reaction vessel, and the mixture is azeotropically reacted at 140℃ until the acid value is ≤15mg KOH / g; the temperature is lowered to 70℃, 6 parts of acrylic acid-terminated polyphosphate are added, and the mixture is reacted until the acid value is ≤8mg KOH / g; 15 parts of hyperbranched polyester Boltron H2O, 5 parts of methyl methacrylate, 3 parts of 2-acrylamide-2-methylpropanesulfonic acid and 0.2 parts of cumene hydroperoxide are added, and the mixture is reacted at 85℃ for 3 hours to obtain a light yellow liquid, which is the modified castor oil; The reinforcing filler comprises the following components by weight: 12-15 parts nano-alumina, 3-5 parts precipitated barium sulfate, and 0.3-0.5 parts fumed silica.

2. The single-component polyurethane coating according to claim 1, characterized in that, The hydroxyl value of the polyether polyol is 300-500 mg KOH / g.

3. The single-component polyurethane coating according to claim 1, characterized in that, The NCO index in the diphenylmethane diisocyanate is 1.05 to 1.

15.

4. The single-component polyurethane coating according to claim 1, characterized in that, The castor oil has a hydroxyl value of 160-168 mg KOH / g and a ricinoleic acid content of ≥85%.

5. The single-component polyurethane coating according to claim 1, characterized in that, The light stabilizer comprises the following components by weight: 0.5 parts of 2-hydroxy-4-n-octyloxybenzophenone and 0.8 parts of hindered amine light stabilizer, wherein the hindered amine light stabilizer is Tinuvin 123 or Tinuvin 292.

6. The one-component polyurethane coating according to claim 1, characterized in that, The organotin catalyst is dibutyltin dilaurate.

7. The one-component polyurethane coating according to claim 1, characterized in that, The reinforcing filler has an average particle size of 20–50 nm for nano-alumina, an average particle size of 0.5–2.0 μm for precipitated barium sulfate, and an average particle size of 10–20 nm for fumed silica.

8. A method for preparing a one-component polyurethane coating as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Add polyether polyol and modified castor oil to a high-speed disperser and mix at 800-1000 rpm for 10 min. During the mixing process, slowly add reinforcing filler. After the reinforcing filler is added, increase the speed to 1500 rpm and disperse for 20-30 min to obtain the premix. S2. Cool the premix to 40°C, add diphenylmethane diisocyanate and organotin catalyst, and react at 500-600 rpm for 60 min to obtain polyurethane prepolymer; S3. Add a light stabilizer to the polyurethane prepolymer and mix at 300-400 rpm for 15 minutes to obtain a primary coating. S4. Transfer the primary coating to a vacuum degassing device for vacuum degassing treatment. The degassing time is 30-60 minutes. Filter the coating through a 200-mesh sieve to obtain the single-component polyurethane coating.

9. The method for preparing a one-component polyurethane coating according to claim 8, characterized in that, The working pressure of the vacuum degassing is 0.02 to 0.09 MPa.

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